Waterproof electronic appliances such as a waterproof mobile phone have become available in recent years.
A mobile phone is described here as an example of an electronic appliance. A type of mobile phone has a main unit and a display unit. The display unit can be opened and closed relative to the main unit. Signals are exchanged between the main unit and the display unit in such a mobile phone through signal lines. For this purpose, the signal lines are routed such that the signal lines extend out of a casing of the main unit into a casing of the display unit. In order to make the mobile phone waterproof, formation of a waterproof structure is important for areas where the signal lines overlap walls of the casings.
A flexible cable integrally formed with rubber or the like, and a flexible cable sandwiched between rubber members or double-sided adhesive tapes, are known as a waterproof structure for such areas. Another example of a known waterproof structure is a structure in which a sealing compound seals a casing hole through which signal lines extend.
The use of rubber, which is suitable for a thin flexible cable, however, does not guarantee waterproofness for separate signal lines, because gaps are created among the signal lines. When using a sealing compound for sealing a hole, it is necessary that the sealing compound flows into the gaps among bundled signal lines. However, determining whether the gaps between the signal lines are sealed with the sealing compound is difficult, which limits the reliability of waterproofness.
Japanese Laid-open Patent Publication No. 2006-93510 discloses a waterproof structure in which a flexible cable and a sealing compound are used. However, the technique disclosed in Japanese Laid-open Patent Publication No. 2006-93510 provides a reliable waterproof structure only when a flexible cable is used. The waterproofing problem occurring when separate signal lines are used is not solved with the technique.
A flexible cable is convenient for connecting, for example, adjacent points in a main unit with adjacent points in a display unit of a mobile phone. However, it is more advantageous, to use separate signal lines that are bundled only between the main unit and the display unit than to use a flexible cable in order to connect remote points in the main unit with remote points in the display unit, except with regard to waterproofness.